For general illumination, large area light sources are often used in order to provide a low peak brightness and hence to give comfortable low-glare lighting. In LED luminaires having an LED array, the small and bright individual LEDs need to be placed relatively far apart on a large area board, such as a printed circuit board, in order to create a large area light source. Usually such a light source is combined with a diffusive plate or foil to hide the individual LEDs.
The trend of LED technology is for smaller LEDs, increased efficiency (and hence lower thermal dissipation) and lower cost. As a result, the LEDs require less PCB area per LED to meet the required thermal and mechanical design constraints. The PCB cost also becomes a more significant part of the total cost (i.e. the Bill Of Materials (BOM)).
One design which has developed as a result of this trend is the so-called E-panel. In such a panel, a rectangular PCB area is halved by cutting the board into two interdigitated (E-shaped) parts that still cover the full area.
This enables two identical substrates to be formed from a single board without wastage of materials. It also enables a shape to be formed which only partially covers the complete area, but without the need to join segments (such as straight line segments) together. A regular array of LEDs can be positioned on the E-shaped board.
As the trend of higher efficiency and lower cost progresses, the E-panels will still have a cost penalty due to unused PCB area. The E-panel design does not for example allow an initial board to be cut into more than two identical parts. The E-panel design is thus not very versatile. There is therefore a need for an alternative design of PCB board, which reduces the unused PCB area.